This proposal describes continuing work on a variety of cells from a wide range of animals, linked by a common aim to correlate fine structural findings with the functional biology of excitable cells. As in previous studies in this laboratory the research plan involves cells of vertebrates and invertebrates, recognizing the opportunity of selecting from the range of zoological types particular cellular systems offering most promise in an approach to basic functional problems, such as intracellular translocation, release of secretory products, synaptic morphogenesis and function and interaction of contractile proteins -- problems that do not observe phyletic divisions. In each facet of the proposed work the information sought either aims to fill an obvious morphological deficiency in our knowledge of cell function or is part of a current or planned collaborative endeavor linking structure and cellular behavior. Much of the work involves nerve and muscle with ancillary studies on non-muscular effectors (luminescent organs and venom-secreting cells) and on mechanisms of secretory release. Studies on axoplasmic architecture, particularly in the lamprey and in giant fibers of arthropods will center upon the role of microtubules in translocation of mitochondria, synaptic vesicle membranes and other components. Analysis of cross-bridging between microtubules and other axoplasmic structures will be extended to the perikaryon, and will include a study of the early effects of vinblastin on this linkage. Studies on synaptic development and function will be conducted on lamprey axons and on an insect luminescent organ. Emphasis is placed on freeze-fracture studies on intramembrane configurations of general occurrence or specifically associated with excitable cells, notably in membranes of normal and denervated frog skeletal fibers. Previous studies on exocytosis in the adrenal will be augmented by studies on ionophore-mediated release of secretion from this mammalian gland and the insect corpus cardiacum. Paramyosin-actin association will be studied in long-sarcomere annelid muscles and actomyosin assemblies of mammalian and mixed origin will be employed to investigate the morphogenesis of muscle contractile systems and of variation in the disposition of actin and myosin filaments in vertebrate and invertebrate fibers.